A reliability enhancement and accelerated testing method for a missile-borne fiber optic gyroscope assembly

Abstract

An enhanced and accelerated reliability testing method for missile-borne fiber optic gyroscope assemblies is disclosed, relating to the field of device reliability testing technology, particularly to the field of reliability testing for missile-borne fiber optic gyroscope assemblies. The high and low temperature operating limits determined through high and low temperature step tests, and the vibration operating limits determined through vibration step tests, provide reliability assessments for the design parameters of the missile-borne fiber optic gyroscope assemblies. Lowering the lower temperature limit from -45℃ to -50℃ and raising the upper temperature limit from 75℃ to 90℃, increasing the temperature change rate from 18℃ / min to 25℃ / min, and changing the vibration load from uniaxial to triaxial six-degree-of-freedom excitation all increase the requirements for reliability assessment of the missile-borne fiber optic gyroscope assemblies, correspondingly shortening the reliability testing time and providing a new option for enhanced and accelerated reliability testing methods.

Description

Technical Field

[0001] This invention relates to the field of reliability testing technology for devices, and in particular to the field of reliability testing technology for missile-borne fiber optic gyroscope assemblies. Background Technology

[0002] In missile guidance systems, a key component is a fiber optic gyroscope assembly. This assembly provides the missile's angle and angular velocity signals in inertial space, providing a basis for missile flight control. The zero-bias and zero-drift parameters of the fiber optic gyroscope assembly are important parameters indicating the product's qualification. After the assembly is manufactured and its zero-bias and zero-drift parameters are tested to be qualified, a reliability assessment test must be conducted before delivery for installation. The typical assessment test method is as follows: holding at the -45℃ operating limit for 20 minutes, then increasing the temperature to 60℃ at 18℃ / min and holding for 100 minutes, then decreasing it to -45℃ at 18℃ / min, and repeating this cycle for variable temperature testing; simultaneously with the variable temperature testing, a single-axis random vibration with an acceleration of 6.06g is added to form a composite test of variable temperature and single-axis random vibration. When the cumulative time of the composite test under the above conditions with the zero-bias and zero-drift parameters meeting the requirements is greater than 461.7 hours, the reliability test is considered passed. The testing method, due to its narrow temperature range, low temperature change rate, short holding time at the operating limit temperature, and the use of single-axis random vibration, fails to fully expose potential faults in the fiber optic gyroscope assembly. This results in a high failure rate where the aforementioned reliability tests are passed but the actual tests fail. Summary of the Invention

[0003] The purpose of this invention is to fully expose the potential faults of fiber optic gyroscope assemblies and reduce the failure rate in actual tests. Therefore, a reliability enhancement and accelerated testing method for missile-borne fiber optic gyroscope assemblies is proposed.

[0004] The technical solution of this invention is as follows: Existing testing methods only consider the temperature and vibration environment of missiles during normal transportation and use, without considering the drastic temperature changes throughout the four seasons during storage, or the severe temperature and vibration changes during short-distance transportation or natural disasters, especially earthquakes. Furthermore, they do not consider the performance degradation caused by component aging after long-term storage. Therefore, the existing testing methods result in discrepancies between the actual performance and the actual performance. To narrow this gap, while maintaining the failure mode, and to avoid direct damage to the fiber optic gyroscope assembly caused by directly increasing stress, a step-stress testing method is adopted to gradually increase the test stress. This fully exposes potential defects in the design and manufacturing process of the missile-borne fiber optic gyroscope assembly, thereby improving its reliability. The implementation steps are: conducting low-temperature step-stress testing and determining the low-temperature operating limit; conducting high-temperature step-stress testing and determining the high-temperature operating limit; conducting five temperature variation tests; conducting vibration step-stress testing and determining the vibration operating limit; and conducting a comprehensive environmental test involving five temperature variation and vibration cycles—a total of five steps.

[0005] The parameters for low-temperature step test and the determination of the low-temperature operating limit are as follows: From -35℃ to -45℃, there are two steps with an interval of 10℃. From -45℃ to -65℃, there are four steps with an interval of 5℃. At each temperature step, after the fiber optic gyroscope assembly reaches temperature stability, the zero bias and zero drift parameters are tested. After passing the test, the temperature is reduced at a rate of 25℃ / min to the next temperature step, and the zero bias and zero drift parameters are tested again. This process is repeated until the temperature step of -65℃. After the fiber optic gyroscope assembly reaches temperature stability, its zero bias and zero drift parameters are tested again. The temperature corresponding to the last step where the parameter tests are passed is its low-temperature operating limit.

[0006] The parameters for high-temperature step test and the determination of the high-temperature operating limit are as follows: From 50℃ to 60℃, there are two steps with an interval of 10℃. From 60℃ to 90℃, there are six steps with an interval of 5℃. At each temperature step, after the fiber optic gyroscope assembly reaches temperature stability, the zero bias and zero drift parameters are tested. After passing the test, the temperature is increased to the next temperature step at a rate of 25℃ / min, and the zero bias and zero drift parameters are tested again. This process is repeated until the temperature step of 90℃. After the fiber optic gyroscope assembly reaches temperature stability, its zero bias and zero drift parameters are tested again. The temperature corresponding to the last step where the parameter tests are passed is its high-temperature operating limit.

[0007] The parameters for the five temperature-variable tests are as follows: Based on the high and low temperature operating limits determined in the above tests, the low temperature limit is the lower limit of the temperature-variable test, and the high temperature limit minus 5℃ is the upper limit of the temperature-variable test. Starting from the lower limit of the temperature-variable test, after the fiber optic gyroscope assembly reaches temperature stability, the zero bias and zero drift parameters are tested. After passing the test, the temperature is increased to the upper limit of the temperature-variable test at a rate of 25℃ / min. After the fiber optic gyroscope assembly reaches temperature stability, the zero bias and zero drift parameters are tested. After passing the test, the temperature is decreased to the lower limit of the temperature-variable test at a rate of 25℃ / min. This process is repeated five times. In the last cycle, the temperature is decreased to room temperature. After the fiber optic gyroscope assembly reaches temperature stability, the zero bias and zero drift parameters are tested.

[0008] Vibration step test parameters and determination of vibration operating limits: After the fiber optic gyroscope assembly is installed on the vibration table, apply a vibration frequency from 5Hz to 10kHz and a vibration stress from 5Grms to 45Grms, with nine steps in total, for a total of nine steps of three-axis, six-DOF non-Gaussian broadband pseudo-random vibration at 5Grms intervals. After holding at each vibration stress step for 10 minutes, perform zero-bias and zero-drift parameter tests on the fiber optic gyroscope assembly. After passing the test, increase the vibration stress step to the next vibration stress step at a vibration change rate of 20Grms / min. Perform zero-bias and zero-drift parameter tests on all vibration stress steps. The vibration value corresponding to the last step where the parameter test is passed is its vibration operating limit.

[0009] Comprehensive environmental assessment of five temperature and vibration cycles: Based on the high and low temperature operating limits, vibration operating limits, and parameters of the five temperature cycles determined in the above tests, each temperature change process is considered a cycle. Three minutes before the temperature change from low to high temperature or high to low temperature, vibration is applied at a rate of 20 Grms / min, with vibration frequencies ranging from 5 Hz to 10 kHz, and vibration stress of [missing value]. The initial vibration stress value of the Grms triaxial six-DOF non-Gaussian broadband pseudo-random vibration was determined by setting the "number of completed temperature change cycles" to zero and substituting it into the above formula. After holding for 15 minutes, its zero bias and zero drift parameters were tested. After passing the test, the temperature was held for another 3 minutes. The same stress was applied and the same test was performed. This cycle was repeated until all five temperature change cycles were completed. After applying vibration for 15 minutes during the ten high and low temperature change processes of all five cycles, the zero bias and zero drift parameters were tested.

[0010] This invention has the following advantages: The high and low temperature operating limits determined by the high and low temperature step test and the vibration operating limits determined by the vibration step test both provide reliability assessments for the design parameters of the airborne fiber optic gyroscope assembly. The low temperature step test, high temperature step test, variable temperature test, and vibration step test added before the comprehensive environmental test of temperature variation and vibration are closer to the actual operating environment of the fiber optic gyroscope assembly. Increasing the temperature change rate from 18℃ / min to 25℃ / min and changing the application of vibration load from uniaxial to triaxial six-degree-of-freedom excitation both raise the requirements for the reliability assessment of the airborne fiber optic gyroscope assembly, and correspondingly shorten the reliability test time, providing a new option for enhanced and accelerated reliability testing methods. Detailed Implementation

[0011] The present invention will now be described in detail with reference to embodiments:

[0012] The following reliability enhancement and acceleration tests were conducted on a certain type of missile-borne fiber optic gyroscope assembly:

[0013] (1) There are two steps from -35℃ to -45℃ with an interval of 10℃. There are four steps from -45℃ to -65℃ with an interval of 5℃. On each temperature step, the holding time from the first step to the third step is 3h, 2h, 1h and 1h respectively. After the zero bias and zero drift parameters are tested, the temperature is reduced to the next temperature step at a rate of 25℃ / min after the test is passed. The zero bias and zero drift parameters test was not passed after holding the temperature for 1h at the fourth step. Therefore, the low temperature operating limit of the missile-borne fiber optic gyroscope combination device is -50℃.

[0014] (2) Two temperature steps are defined, with each step from 50℃ to 60℃ in 10℃ increments. Six temperature steps are defined, with each step from 60℃ to 90℃ in 5℃ increments. At each temperature step, the holding times from the first to the eighth step are sequentially 3h, 2h, 1.5h, 1.5h, 1.5h, 1.5h, 1h, and 1h, followed by zero-bias and zero-drift parameter tests. The temperature is then increased to the next step at a rate of 25℃ / min, and the zero-bias and zero-drift parameter tests are repeated until the temperature reaches 90℃. After the fiber optic gyroscope assembly reaches temperature stability, its zero-bias and zero-drift parameters are tested, and the tests are passed. Therefore, the high-temperature operating limit of this missile-borne fiber optic gyroscope assembly is 90℃.

[0015] (3) Based on the low temperature limit of -50℃ and the high temperature limit of 90℃ determined by the above test, with -50℃ as the lower limit of the temperature change test and 85℃ as the upper limit of the temperature change test, the test is carried out starting from -50℃. After the fiber optic gyroscope assembly is kept at the temperature for 3 hours, the zero bias and zero drift parameters are tested. After the test is passed, the temperature is increased to 85℃ at a rate of 25℃ / min. After the fiber optic gyroscope assembly is kept at the temperature for 3 hours, the zero bias and zero drift parameters are tested. After the test is passed, the temperature is decreased to -50℃ at a rate of 25℃ / min. This process is repeated five times. The last cycle is cooled to room temperature. After the fiber optic gyroscope assembly reaches temperature stability, the zero bias and zero drift parameters are tested and passed. The test is passed after five temperature change tests.

[0016] (4) After the fiber optic gyroscope assembly was installed on the vibration table, a three-axis, six-DOF non-Gaussian broadband pseudo-random vibration was applied with a vibration frequency ranging from 5Hz to 10kHz and a vibration stress ranging from 5Grms to 45Grms, with each step spaced at 5Grms, for a total of nine steps. After maintaining the vibration stress step for 10 minutes at each step, the fiber optic gyroscope assembly was tested for zero bias and zero drift parameters. After passing the test, the vibration stress step was increased to the next step at a vibration change rate of 20Grms / min. The zero bias and zero drift parameter tests performed on all vibration stress steps were qualified, and the vibration stepping test was qualified. Therefore, the vibration operating limit of this airborne fiber optic gyroscope assembly is 45Grms.

[0017] (5) Based on the low temperature working limit of -50℃, the high temperature working limit of 90℃ and the vibration working limit of 45Grms determined by the above test, each temperature change process is a cycle. Three minutes before the temperature change from -50℃ to 85℃ or from 85℃ to -50℃, vibration is applied at a vibration change rate of 20Grms / min. The vibration frequency ranges from 5Hz to 10KHz. The vibration stress applied during the temperature change process in the five cycles is 8Grms, 16Grms, 24Grms, 32Grms and 40Grms respectively. It is a triaxial six-degree-of-freedom non-Gaussian broadband pseudo-random vibration. After holding for 15 minutes, its zero bias and zero drift parameters are tested. After passing the test, the temperature is held. The same stress is applied 3 minutes before the next temperature change, and the same test is performed. This cycle is repeated until all five temperature change cycles are completed. The zero bias and zero drift parameters tested 15 minutes after applying vibration in all five cycles are qualified, which means that the comprehensive environmental test of five temperature change and vibration is passed.

[0018] Through the implementation of enhanced and accelerated reliability testing of a certain type of airborne fiber optic gyroscope assembly, the low-temperature operating limit of the temperature stress was widened from the design-specified -45℃ to -50℃, and the high-temperature operating limit was widened from the design-specified 75℃ to 90℃. The temperature change rate was increased from 18℃ / min to 25℃ / min, and the holding time at the operating limit temperature was increased from 120 min to a product temperature stabilization time of 180 min. Triaxial six-degree-of-freedom excitation vibration was adopted, which not only improved the efficiency of fault induction in the test method but also avoided damage caused by directly increasing the stress on the product by gradually increasing the stress through a step stress method. A total of 30 potential defects were exposed during the test, covering all failure modes that occurred in the actual application of this type of product. The improved product's low-temperature operating limit was increased by 5℃, and the high-temperature operating limit was increased by 15℃. The reliability test time was shortened from 461.7 hours to 85 hours, providing a new option for enhanced and accelerated reliability testing methods.

Claims

1. A reliability enhancement and accelerated testing method for a missile-borne fiber optic gyroscope assembly, characterized in that: The process involves five steps: low-temperature step-by-step testing to determine the low-temperature operating limit, high-temperature step-by-step testing to determine the high-temperature operating limit, five temperature variation tests, vibration step-by-step testing to determine the vibration operating limit, and a comprehensive environmental assessment involving five temperature variation tests and vibration tests. The first step, the low-temperature step-by-step testing parameters and the scheme for determining the low-temperature operating limit, are as follows: two steps from -35℃ to -45℃ with 10℃ intervals, and four steps from -45℃ to -65℃ with 5℃ intervals. At each temperature step, after the fiber optic gyroscope assembly reaches temperature stability, zero-bias and zero-drift parameter tests are performed. After passing the test, the temperature is reduced at a rate of 25℃ / min to the next temperature step, and then the zero-bias and zero-drift parameter tests are performed again. The first step involves gradually increasing the temperature to -65℃. After the fiber optic gyroscope assembly reaches temperature stability, its zero-bias and zero-drift parameters are tested. The temperature corresponding to the last step where the parameters pass the test is its low-temperature operating limit. The second step involves high-temperature stepping tests and determining the high-temperature operating limit as follows: from 50℃ to 60℃, there are two steps in 10℃ increments; from 60℃ to 90℃, there are six steps in 5℃ increments. At each temperature step, after the fiber optic gyroscope assembly reaches temperature stability, zero-bias and zero-drift parameters are tested. After passing the test, the temperature is increased at a rate of 25℃ / min to the next temperature step, and the zero-bias and zero-drift parameters are tested again, until the temperature reaches 90℃. After the fiber optic gyroscope assembly reaches temperature stability, its zero-bias and zero-drift parameters are tested. The temperature corresponding to the last step of the parameter test that passes is its high-temperature operating limit. The third step, the five-time temperature variation test, is as follows: Based on the determined high and low temperature operating limits, the low temperature limit is the lower limit of the temperature variation test, and the high temperature limit minus 5°C is the upper limit. Starting from the lower limit of the temperature variation test, after the fiber optic gyroscope assembly reaches temperature stability, the zero-bias and zero-drift parameters are tested. After passing the test, the temperature is increased to the upper limit of the temperature variation test at a rate of 25°C / min. After the fiber optic gyroscope assembly reaches temperature stability, the zero-bias and zero-drift parameters are tested again. After passing the test, the temperature is decreased to the lower limit of the temperature variation test at a rate of 25°C / min. This process is repeated five times. In the last cycle, the device is cooled to room temperature. After the fiber optic gyroscope assembly reaches temperature stability, the zero bias and zero drift parameters are tested. The parameters for the fourth step of vibration stepping assessment and the scheme for determining the vibration working limit are as follows: After the fiber optic gyroscope assembly is installed on the vibration table, a three-axis, six-degree-of-freedom non-Gaussian broadband pseudo-random vibration with a vibration frequency from 5Hz to 10KHz and a vibration stress from 5Grms to 45Grms is applied. Each step is 5Grms apart, for a total of nine steps. After holding each vibration stress step for 10 minutes, the zero bias and zero drift parameters of the fiber optic gyroscope assembly are tested. After passing the test, the vibration change rate is increased to the next vibration stress step at 20Grms / min.Zero bias and zero drift parameter tests are performed on all vibration stress steps. The vibration value corresponding to the last step that passes the parameter test is its vibration working limit. The fifth step is a comprehensive environmental assessment scheme for five temperature and vibration changes: based on the determined high and low temperature working limit values, vibration working limit, and parameters of the five temperature changes, each temperature change process is a cycle. Three minutes before the temperature change from low temperature to high temperature or from high temperature to low temperature, vibration is applied at a vibration change rate of 20 Grms / min, with a vibration frequency from 5 Hz to 10 kHz and a vibration stress of 10 kHz. The initial vibration stress value of the Grms triaxial six-DOF non-Gaussian broadband pseudo-random vibration was determined by setting the "number of completed temperature change cycles" to zero and substituting it into the above formula. After holding for 15 minutes, its zero bias and zero drift parameters were tested. After passing the test, the temperature was held for another 3 minutes before the next temperature change, and the same stress was applied and the same test was performed. This cycle was repeated until all five temperature change cycles were completed. After applying vibration for 15 minutes during the ten high and low temperature change processes of all five cycles, the zero bias and zero drift parameters were tested.

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